Most accidents that occur in and around loading docks are attributable to human error. These accidents can result in serious injury, especially when power material handling equipment is used. Often these accidents are the result of a failure to properly secure the parked truck in place, coupled with an inattentive driver who prematurely drives away while workers and/or equipment are still engaged in the loading or unloading operations. In addition to premature departure, other circumstances can lead to undesired separation of the trailer from the dock, such as trailer creep or landing gear collapse. Accordingly, vehicle restraint devices were developed.
Vehicle restraint devices are generally well known in the art, and are routinely employed in order to effectively secure a vehicle to an adjacent loading dock during loading and unloading operations. Although the design, cost and effectiveness of existing vehicle restraints differs widely, if properly designed, such restraint devices can help reduce the number of serious injuries resulting from human error in the loading dock environment.
One such vehicle restraint device employs a rotating hook which engages the ICC bar (also called a Rear Impact Guard or RIG) on the rear of the truck. As shown in FIG. 1, the hook 1 of this type of prior art vehicle restraint is typically mounted in a carriage 2 which is slidably mounted to the dock structure and which automatically adjusts to the height of the RIG as a vehicle approaches the structure. A motor (not shown) rotates the hook 1 from a retracted position to an engaged position in which the hook 1 engages or captures the RIG. The typical hook 1 consists of a crown 4 and a shank 5, with the shank 5 having a longitudinal axis 6 which intersects the pivot point 7 of the hook 1. Such a conventional design limits the hook 1 to a simple, rotational movement about the pivot point 7. Examples of such rotating hook vehicle restraint devices can be found in U.S. Pat. Nos. 4,264,259 and 4,379,354. Vehicle restraint devices of the rotating hook variety are generally viewed as the most effective approach to preventing certain loading dock accidents, such as unscheduled departure, trailer creep, landing gear collapse, or trailer upending.
The size and strength of the RIG is subject to regulation by the National Highway Traffic Safety Administration (NHTSA). Recently, the NHTSA has issued new regulations increasing the strength requirements for the RIGs installed on newly manufactured vehicles. One way to achieve the new strength requirements, although not required under the rule, is to increase the cross-sectional dimensions of the RIG, for example, by increasing the vertical dimension. Unfortunately, the existing hooks on many vehicle restraint devices (of both the rotating hook design and other varieties) were not designed for these taller (up to 6") RIGs. In the case of rotating hook restraints, these taller RIGs may, in certain limited circumstances, render existing hooks incapable of achieving the functionally advantageous "two-point contact" trap when the existing hooks are used with the new taller RIGs. Although the dimensions of the hook could be increased in order to obtain the "two-point contact" trap for a taller RIG, increased material costs for an oversize hook, along with the need for a larger motor to rotate the oversize hook, make this an undesirable approach. Moreover, on most devices, larger hooks cannot be retrofitted because such larger hooks are not capable of being fully retracted within the moveable carriage and may thus interfere with the carriage's normal range of motion and operation.
Accordingly, there exists a need for an improved vehicle restraint device including a rotating restraining member capable of capturing the newer and larger ICC bars, yet also capable of retracting fully within the carriage of an existing vehicle restraint device.